(a) Field of the Invention
The present invention relates to a dimming angle sensing circuit and a driving method thereof.
(b) Description of the Related Art
A triac dimmer passes each cycle of a sine wave of an AC input by a dimming angle. In order to maintain the train dimmer in a turn-on state, more than a predetermined holding current should flow through the dimmer.
In further detail, when a dimmer is controlled to control brightness of lighting, an output current supplied to the lighting should be controlled according to a dimming angle. That is, the lighting should be more bright as the dimming angle is increased, and the lighting should be more dark as the dimming angle is decreased.
The power supply needs information on a dimming angle to supply an output current to the lighting according to the dimming angle. Otherwise, the power supply generates a constant output current without regard to the dimming angle, thereby causing an undesired increase of a switching duty of the power supply.
For example, although the dimming angle is controlled to be 90 degrees in order to decrease the brightness of the lighting to the half, the power supply may increase the switching duty to supply the output current as much as when the dimming angle is 180 degrees.
As described, information on a dimming angle is required, and typically, a digital circuit is used to sense and calculate a dimming angle. The digital circuit includes a switch to sense a dimming angle. However, a switching noise may occur during sensing of the dimming angle due to switching operation of the switch.
Further, the resolution of the digital circuit may be increased to accurately sense the dimming angle and thus the size of the digital circuit may be increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.